An apparatus for controlling the attitude of onboard units by driving an electric motor or motors is currently known in various forms. For example, U.S. Pat. No. 4,503,504 discloses an arrangement including a microcomputer for attitude control.
However, it is to be noted that an automobile is recently provided with an increasing number of units or target objects, the attitude of which are to be controlled. By way of example, a driver's seat is associated with a sliding mechanism which positions the seat in the fore-and-aft direction, a front vertical mechanism which adjusts the elevation of the front portion of the seat, a rear vertical mechanism which adjusts the height of the rear portion of the seat, a reclining mechanism for a seat back, a head rest elevation adjusting mechanism or the like, all of which may be driven by electric motors. A tilting mechanism and a telescopic mechanism which are mounted on a steering column to adjust the position of a steering wheel can also be driven by electric motors. Most automobiles are provided with a mechanism which adjusts the position of individual mirrors in the vertical and lateral directions.
When these mechanisms are to be driven by electric motors, it is preferable that a microcomputer be used as a controller. Specifically, the use of a microcomputer enables a variety of safety units to be provided, a number of attitudes to be stored, and allows these units to be driven to selected ones of stored proper positions or attitudes through a single switch operation.
However, it is undesirable that all of a number of onboard attitude control mechanisms be controlled by a single microcomputer. This is because if the task required far exceeds the processing capability of the microcomputer, an increased length of time will be required to execute a single operation, and there will be an increased length of time interval between successive operations, causing a time lag in the control. Thus, it takes a long time until the attitude or position control is actually initiated after a switch operation has been made, or the actuation of a security function may be delayed to cause damage to a unit or units. In addition, when a single controller is used to control a plurality of mechanisms which are widely spaced apart on a vehicle, electric cables of increased lengths must be used to connect the controller with a number of electrical components such as switches, motors, position sensors or the like on these mechanisms which are located at distances from the controller.
A time lag in the control may be reduced by utilizing a plurality of controllers such as microcomputers so that each mechanisms may be controlled by a separate controller, thus reducing the task assigned to each controller. This also allows the independent controllers to be located adjacent to each associated mechanisms with a concomitant reduction in the cable length required. For this reason, a plurality of controllers have been used in the prior art when the position or attitude of various mechanisms are to be controlled electrically.
The attitudes of the seat, the steering wheel and a mirror or mirrors should all be changed in accordance with the physical configuration of a driver or his seating condition. Accordingly, a plurality of proper attitudes corresponding to a plurality of drivers may be stored, and one of these stored attitudes may be retrieved in response to a switch operation. In this instance, switches which are used to issue such command may be used in common to control the attitudes of the seat, the steering wheel and the mirrors. In other words, when a single switch is capable of issuing a command to retrieve one of stored attitudes, such switch may be connected to a seat attitude controller, a steering wheel position controller and a mirror attitude controller in common, thus providing commands t control the attitudes of all of the seat, the steering wheel and the mirror by a single switch operation.
However, when independent controllers are used with individual different mechanisms, and a single attitude controlling switch is connected to the plurality of controllers in common, an inconvenience is experienced. Specifically, since the different controllers operate asynchronously, the status of a single switch will be read at different timings by different controllers. Thus, when a driver turns on the switch for a brief interval, one of the controllers may successfully reads the on status of the switch while the others may fail to read same. In such instance, if a drive operates an attitude controlling switch and the attitude of the seat is properly executed, the position of the mirror may remain uncontrolled. This brings forth a difficulty that the driver may be possessed with an idea that the attitude control is complete, and may notice that the mirror is in an improper position after he has started his vehicle, presenting a difficulty in his driving maneuver.